Method and apparatus for stacking thin sheets in an even-edged stack



June 23, 1970 L R, JR" ET AL 3,516,658

METHOD AND APPARATUS FOR STACKING THIN SHEETS IN AN EVEN-EDGED STACK Filed June 4. 1968 2 Sheets-Sheet 1 m m N T q:

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METHOD AND APPARATUS FOR STACKING THIN SHEETS IN AN EVEN-EDGED STACK Filed June 4. 1968 2 Sheets-Sheet :2

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New 0. edge, 21y 6:444:14 Wflitoaneys United States Patent 3,516,658 METHOD AND APPARATUS FOR STACKING THIN SHEETS IN AN EVEN-EDGED STACK Ruel E. Taylor, Jr., West Buxton, and Norman C. Wedge, Gorham, Maine, assignors to Scott Paper Company, Delaware County, Pa., a corporation of Delaware Filed June 4, 1968, Ser. No. 734,384 Int. Cl. B65h 31/16 US. Cl. 271-88 4 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION This invention relates to product handling means, more particularly to apparatus for lowering a growing vertical stack of thin sheets at a predetermined rate, equal to, and along the path of, stack growth. The primary application for this invention is in stacking sheets of paper in a layboy to obtain a finished stack which can be sold without further trimming, restacking or other finishing operations.

The invention is useful in any application where thin sheets are to be stacked in an even-edged stack.

Prior art devices of this type operate intermittently to lower the stack in sudden discrete movements as it grows in response to a sensing device adjusted to restore the top of the stack to a given level. Such intermittent or cyclical operation has three primary undesirable effects.

First, between cycles, growth of the stack causes a displacement of the top of the stack from its optimum receiving position and this results in a proportional misv alignment in each sheet as it is deposited on the stack.

Second, as the lowering takes place, the sudden repositioning of the stack to the starting position causes an unevenness of the sheet or sheets stacked during and after the movement, relative to those already on the stack. To

fully appreciate the efiect of this unevenness, it is important to realize that as a stack of paper grows it takes on a distinctive topology of gently sloped mounds and valleys. Sheets which are evenly stacked are held securely in place by total contact with the sheets above and below 1 in accordance with the topology. An unevenly stacked sheet cannot assume the topology due to its relative dislocation with respect to the contiguous sheets, thus creating a new topology. This interface which does not provide total contact for the surface of the sheet will further dislocate on succeeding repositioning of the stack as well as during shipment. Therefore, small unevenness which are in themselves undesirable often become dislocations of such magnitude that the product is unsuitable for sale without further trimming or restacking.

The third undesirable effect is that the sudden, intermittent repositioning of the stack causes considerable shock and stress on the machinery which may result in shortened life and higher maintenance costs, but in addition, causes flexure of the stack and the platform thus contributing to the unevenness. This effect is particularly apparent as the stack approaches its final height at which time it may weigh as much as three tons.

In G. Forrester US. Pat. No. 3,310,169, a hydraulic elevator is described which is intermittently lowered by bleeding in response to a relay operated valve activated by a photoelectric device which senses the top of the stack. This device cannot produce the even ed ed stack of which the present invention is capable due to the sudden movements of the elevator in response to the activation of the relay by the photoelectric sensor.

S. M. Obenshain, US. Pat. No. 3,203,326, describes a photoelectric control device in a sheet packet delivery stacking system which also operates on an intermittent basis.

In the present invention, the photoelectric device is absent, the control being achieved by coordinating a continual bleeding of the hydraulic cylinder to a rate equal to the rate of growth of the stack.

SUMMARY OF THE INVENTION In the present invention, hydraulic cylinders are in actuating association with the platform which supports the stack. A constant-flow control valve is connected to the cylinders to permit continual bleeding of hydraulic fluid from the cylinders at a predetermined rate by adjustment of the valve. Fluid exiting from the valve flows to a reservoir where it is stored and available to be pumped back into the cylinders.

The valve is adjustable to allow the platform to descend continually at a rate in precise coordination with the rate of growth of the stack.

A solenoid actuated on/off valve is also incorporated which is associated with the adjoining machinery which feeds sheets to the stack in such a manner that when feeding stops, the solenoid is actuated to stop descent of the stack.

In view of the foregoing it is the general object of the present invention to provide an apparatus and method of the above described type which will allow the stacking of thin sheets in an even-edged stack.

Another object is to provide an improved means for precisely maintaining the position of the top of a growing stack in relation to the device which feeds the stack.

Another object is to provide means for lowering a growing stack along the path of stack growth by continual motion.

An additional object is to provide means of stopping movement of the stack when feeding from adjacent machinery stops.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation view of the preferred embodiment of the invention showing the platform and hydraulic cylinder lowering apparatus for a stack of sheets in relation to incoming sheets;

FIG. 2 is a front elevation view of the apparatus of FIG. 1 showing the platform and hydraulic cylinder lowering apparatus with portions broken away to show the relationship of the rear lowering supports;

FIG. 3 is a diagrammatic view of the preferred embodiment of the hydraulic system illustrating the method of control of the hydraulic cylinders; and

FIG. 4 is a top plan view of the apparatus of FIG. 1 showing the hydraulic cylinder lowering apparatus and the relationship of the chains and sprockets.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1, 2, and 4, stack 1 is the final product of the paper finishing process composed from a stream of sheets 2, applied sequentially and being rapidly delivered in overlapped position from an adjacent overlap feed conveyor 3. The stack is laid on a platform 4 which is supported at four corners by identical pairs of chain supports 5 and 5A. The suspended length of the portion of chain supports 5 and 5A which suspends the platform 4 is adjusted through a series of sprockets by vertical movement of a pair of hydraulic rams 6 in hydraulic cylinders 7. The entire stacking apparatus is generally referred to in the paper making industry as a layboy which is the term used herein.

The chains extend from the platform 4 over idler sprockets 19 and 20 to a twin ram sprocket 21 and finally are fixed to the machine frame by turnbuckles 22. The chains 5A similarly extend from the platform 4 over idler sprockets 23 and 24 to the twin ram sprocket 21 and finally are fixed to the machine frame by the turnbuckles 25. This arrangement has been found to provide for smooth operation of the layboy in a compact structure.

FIG. 3 shows the hydraulic system for raising and lowering the platform 4. A bleed line 8 is connected to the hydraulic cylinders 7 and runs through a valve 18 to a constant flow metering valve 10. The constant flow valve 10 has mounted thereon a flow indicator 11 which comprises a scale 12 and flow indicia 13. The constant flow valve 10 also has a needle valve 14 whose function will be made clear below. Fluid passing through the valve 10 and indicator 11 is returned to a sump 9 by line 8. The units numbered 10-14 may be, for example, of the same general type as the Rotameter devices manufactured by Brooks Instrument Co. and their associated flow controller type 8802.

The valve 18 is an on/ofi type which is actuated by a solenoid 16. The solenoid 16 is connected as represented by line 17 to be energized during the periods the stop/ start control of the overlap feed conveyor 3 of FIG. 1 is running to deliver the stream of overlapped sheets to the layboy.

Hydraulic fluid from the sump 9 is supplied under pressure by a pump to a two way valve 15a. When positioned opposite to that shown in FIG. 3, the valve 15A supplies pressure fluid from the pump 15 to the cylinders 7 via a check valve 15B. In the position shown in FIG. 3 the valve 15A disconnects pump pressure from the check valve 15A and bleeds the pressure in the line to the sump 9 thus permitting the check valve 15B to close. The valve 15A may be manually operated as indicated in FIG. 3.

In operation the layboy platform 4 is initially moved by applying pressure from pump 15 through valve 15A to cylinder 7 to a raised position adjacent to the overlap feed conveyor 3 to receive the sheets 2. When the overlap feed conveyor 3 is started the solenoid 16 is simultaneously energized to actuate the on/ofl valve 18 permitting fluid to flow from the hydraulic cylinders 7 through 7 the constant flow valve 10, the flow indicator 11 and finally to the sump 9. The bleeding of fluid from the cylinders 7 causes the platform 4 to descend. The constant flow valve 10 provides that fluid flows at a constant rate and thus causes the platform 4 to descend at a constant rate regardless of the weight or height of the stack 1. In the absence of the constant flow valve 10, the platform 4 would tend to descend at an increasing rate as the weight of the stack increased.

The needle valve 14 in the constant flow valve 10 permits adjustment of the constant flow rate so that the rate of descent of the platform 4 can be coordinated precisely with the rate of growth of the stack 1. By this means the top of the stack 1 may be kept at the optimum position for receiving sheets 2 from the overlap feed conveyor 3. The proper setting of valve 14 for any given rate of stack growth may be made by observation or, if desired, the flow indicator 11 can have the scale 12 calibrated in terms of the rate of feed of sheets. Then as the needle valve 14 is adjusted the indicator 13 may be placed adjacent the scale setting corresponding to the feed rate.

When the stack 1 has reached its desired height the apparatus is stopped and the stack removed. The platform completed the check valve 15B is closed by manually switching the pressure relief valve 15A to a bypass position (shown in FIG. 3) relieving pressure on the upstream side. of the check valve 15B.

It is intended to cover all changes and modifications of the preferred embodiment herein chosen for purposes of the disclosure which do not constitute departures from the spirit and scope of the invention as defined in the appended claims.

We claim: 1. Apparatus for stacking thin flexible sheets delivered at high speed in an even-edged stack comprising:

a layboy having a vertically movable platform for receiving the delivered sheets;

hydraulic actuator means operable upon application of hydraulic pressure for raising said platform in said layboy;

control means for selectively applying hydraulic pressure to said actuator;

a bleed line for said actuator means;

valve means operable for opening said bleed line to bleed hydraulic fluidfromsaid actuator means to lower said platform; and

constant flow rate'metering means in said bleed line selectively operable for obtaining a range of constant flow rates for fluid bled from said actuator means which flow rates are independent of load on said platform. 1

2. Apparatus according to claim 1 and including a flow .rate indicator in said bleed line.

.steps of:

delivering said sheets substantially horizontally and arresting said sheets at the end of said stream;

supporting the arrested sheets on a support, the vertical position of which is adjustable relative to the point of delivery;

maintaining the adjusted vertical position of said support by hydraulic fluid pressure to make said vertical position independent of the weight of the stack of sheets on said support;

bleeding hydraulic fluid at a constant flow rate to obtain a uniform rate of descent for said support; and

adjusting said constant flow rate to make said rate of descent correspond with the rate of growth in the height above said support of the stack of sheets received from said moving stream.

References Cited UNITED STATES PATENTS 2,636,933 4/1953 Lecher 27188 FOREIGN PATENTS 551,913 1/1958 Canada.

EVON C. BLUNK, Primary Examiner R. S. GAITHER, Assistant Examiner 

